Heat resistant UV blocking coatings are known in the art. For example, see U.S. patent documents U.S. Pat. No. 5,480,722 and 2002/0122962A1.
Wet chemical routes to produce heat resistant UV blocking coatings based on cerium oxide are known. Cerium oxide also may be combined with silica and/or titania to enhance the quality of the films. For instance, the addition of titania further enhances the UV blocking efficiency of ceria. Unfortunately, however, the resulting films tend to produce a yellowed transmitted color. Also, the refractive index of ceria-titania composite coatings tend to be significantly higher than that of flat glass substrates, which are normally used to support deposited coatings for window applications. As a result, these coatings tend to be highly reflective and also tend to exhibit an interference color pattern, which are generally undesirable for window applications.
In order to suppress these undesired effects, multi-layer oxide coatings of varying indexes have been tried. Unfortunately, however, the application of multiple oxide layers is not attractive for commercial applications, including wet chemical methods, because of the complexity of manufacturing processes and associated higher yield losses.
Interference effects of high refractive index ceria-titania coatings also may be reduced by increasing coating thickness. Unfortunately, however, thicker coatings tend to be undesirably yellow.
The addition of silica to ceria and ceria-titania coatings also could significantly reduce the refractive index of the coatings. Thus, reflection and interference effects of the resultant coatings could be reduced. Because silica is transparent in the UV region, the addition of higher levels of silica to ceria-based coatings increases coating thickness requirements in order to achieve adequate UV blocking. The higher the thickness, however, the greater the tendency for coatings to develop micro-cracks during high temperature heat treatment processes such as, for example, tempering and heat strengthening of glass substrates.
In view of the foregoing, it will be appreciated that there is a need in the art for UV blocking coatings having enhanced UV blocking efficiency, aesthetic appearances that have reduced amounts of undesirable optical effects (such as yellowish color, interference patterns, etc.), and that are less likely to develop micro-cracks after high temperature heat treatment. It also will be appreciated that there is a need in the art for methods of making the same.
The term “substantially crack-free” does not imply the absence of all cracks; rather, it means that to the extent that any cracks form in the coating during production, the cracks (if any) do not substantially interfere with the overall structure, function, and operation of the UV coating, either alone or in the layered stack.
In certain example embodiments of this invention, a method of making a coated article is provided. A glass substrate is provided. A base coat is curtain coated on the glass substrate, with the base coat including zinc, cerium, titanium, and silicon. The base coat is cured. A top coat is roll coated, directly or indirectly, on the base coat, with the top coat being a sacrificial cross-linked organic polymer-based layer. The substrate is heat treated with the base coat and the top coat thereon. The base coat and the top coat vary in thickness by no more than 15% prior to the heat treating.
In certain example embodiments of this invention, a method of making a coated article is provided. A glass substrate is provided, with the glass substrate having thereon (a) a base coat curtain coated from an oxide precursor material including zinc, cerium, titanium, and silicon, and (b) a sacrificial cross-linked organic polymer-based top coat roll coated on the base coat. The substrate is heat treated with the base coat and the top coat thereon, with the heat treating removing substantially all of the top coat from the base coat and causing substantially no cracks to form in the base coat. The base coat is formed from an oxide precursor comprising 40-80 mol % zinc, 5-50 mol % ceria and titania, and 0-10 mol % silane. The base coat and the top coat vary in thickness by no more than 10% prior to the heat treating.
In certain example embodiments of this invention, a coated article is provided. The coated article includes a glass substrate. A base coat is on the glass substrate, with the base coat including zinc, cerium, titanium, and silicon and being curtain coated from an oxide precursor material. A sacrificial cross-linked organic polymer-based top coat is roll coated on the base coat. The substrate with the base coat and the top coat thereon are heat treatable such that substantially all of the top coat is removable from the base coat while causing substantially no cracks to form in the base coat. The base coat is formed from an oxide precursor comprising 40-80 mol % zinc, 5-50 mol % ceria and titania, and 0-10 mol % silane. The base coat and the top coat are applied so as to vary in thickness by no more than 5% prior to any heat treatment.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.